Proto-Slavic *bojь

→ Czech boj (inherited)

→ Old Church Slavonic болꙗринъ (inherited)

→ Macedonian бој (inherited)

→ Macedonian боен (mention)

→ Macedonian боиште (mention)

→ Polish bój (inherited)

→ Romanian bai (derived)

→ Russian бой (inherited)

→ Serbo-Croatian boj (inherited)

→ Serbo-Croatian бој (inherited)